High Serum HDGF Levels Are Predictive of Bone Metastasis and Unfavorable Prognosis in Non-Small Cell Lung Cancer

Hepatoma-derived growth factor (HDGF) is a heparin-binding protein possessing mitogenic activity and could be secreted from necrotic cells passively or actively, thereby functioning as a damage-associated molecular pattern (DAMP). The high expression of HDGF in non-small cell lung cancer (NSCLC) tissues is associated with unfavorable prognosis. However, the clinical significance of serum HDGF has not been elucidated in NSCLC yet. In the present study, we compared the serum levels of HDGF in 235 patients with NSCLC (141 adenocarcinoma and 94 squamous cell carcinoma cases) with those in 40 healthy subjects. Moreover, we explored the correlation between serum HDGF levels and clinicopathologic factors or the overall survival rates. We thus found that the serum HDGF levels were significantly higher in NSCLC patients than those in healthy subjects (P < 0.001). Moreover, there was no significant difference in the serum HDGF levels between adenocarcinoma and squamous cell carcinoma. Importantly, the higher serum levels of HDGF were significantly associated with bone metastasis and with lower overall survival rates. Thus, serum HDGF was identified as an independent prognostic factor indicating poor prognosis of NSCLC. Using A549 human lung adenocarcinoma cell line, we demonstrated that an autophagy inhibitor, chloroquine, could inhibit the HDGF secretion, while quercetin, an autophagy inducer derived from a traditional Chinese drug, could facilitate HDGF secretion. In conclusion, high serum levels of HDGF were significantly correlated to bone metastasis and poorer prognosis of NSCLC. We suggest that anti-HDGF therapy is potential to protect NSCLC patients with advanced stages from bone metastasis.